Racemic rabeprazole is chemically known as 2-[[[4-(3-methoxypropoxy)-3-methyl-2-pyridinyl]methyl]sulfinyl]-1H-benzimidazole and is represented as follows:

EP0773940 describes the preparation of R-(+)-rabeprazole and S-(−)-rabeprazole. Separation of racemic rabeprazole into R-(+)-rabeprazole and S-(−)-rabeprazole by chromatography has been described by Nochi et al in Chem. Pharm. Bull. 44, 1853-1857 (1996). Dexrabeprazole is known as R-rabeprazole.
WO9955157 and WO9955158 describe various formulations of R-(+)-rabeprazole and S-(−)-rabeprazole, respectively.
Various salts such as calcium, sodium, zinc and nitrate of racemic rabeprazole have been disclosed in different patents. WO0104109 claims Li, Na, K, Mg, Ca, Ti and quaternary ammonium salt of racemic rabeprazole. The most commonly-used salt of racemic rabeprazole is the sodium salt.
WO2007041790 and WO2004060263 simply mention the existence of the isomers of rabeprazole while describing the magnesium salt of rabeprazole. Neither of these applications discloses examples of the preparation of the magnesium salt of dexrabeprazole.
The sodium salt of dexrabeprazole is known and available commercially. However, the sodium salt of dexrabeprazole is not stable over a long period of time. Also it is hygroscopic in nature. This makes the storage and handling of the dexrabeprazole sodium difficult and also it is further difficult to formulate dexrabeprazole sodium in a suitable dosage form.
Hence, there was a need to develop a stable salt of dexrabeprazole which can be stored as well as easily formulated into dosage form.